The Hahn lab seeks to identify and functionally validate new kinase oncogenes that will be valuable targets for cancer therapy. In our recent work, we have initiated a large-scale effort to integrate high throughput functional genomic approaches with experimental models of human cell transformation and comprehensive structural characterization of cancer genomes to identify the novel breast oncogene, Inhibitor of KB kinase e (IKBKE, IKKe, IKKi). IKBKE is amplified and overexpressed in a substantial subset of human breast cancer cell lines and tumors, is required for the proliferation and viability of breast cancer cell lines that harbor IKBKE copy number gain, and confers a tumorigenic phenotype in two different experimental models of human cell transformation that depend upon constitutively active AKT signaling. Cancer cell lines and tumors that overexpress IKKe exhibit increased NF-KB activity, which is essential for the transformed phenotype. Despite our preliminary mechanistic understanding of the role of IKKe in breast cancer, the specific substrates of IKKe necessary for the transformed phenotype have not yet been identified. Here I propose to dissect the downstream biochemical pathway by which IKKe mediates cell transformation. I will first use traditional immnoprecipitation to determine whether known IKKe- protein interactions occur in IKKe- transformed human mammary epithelial cells (HMECM). An unbiased approach will also be taken with high- throughput screening of a positional peptide library to identify IKKe phosphorylation substrates. Ultimately, I will assess the functional relevance of putative IKKe targets identified by these approaches. Additionally, in follow up to a recent discovery that IKKe is ubiquitinated independently proteasomal degradation, I also seek to confirm and characterize this modification by mass spectrometry and assess whether IKKe ubuitination contributes to it ability to mediate NF-KB activation, anchorage independent growth and tumor formation in immunodeficient mice. These studies will elucidate dynamic components of the IKKe pathway which potentially represent attractive targets for therapeutic drug development in breast cancer. Although much progress has been made in breast cancer research, mechanisms underlying the initiation of non-hereditary breast cancer have not been fully elucidated. We have identified a new molecule, IKKe, that is involved in the development of breast cancer. We plan to define its mechanism of action in causing breast cancer in effort to potentially develop a new anti-cancer drug.